The present application relates to a magnet structure to create the bias magnetic field in a bubble memory device. More particularly, the present invention consists of a single bias field magnet made of a single material and in thermal contact with the bubble memory chip, the entire structure being placed within the rotating field drive coils of a bubble memory device.
Prior art magnetic bubble memory devices require a pair of magnets, each associated with a high permeability leveling plate, within a shielding structure and having the bubble memory chip and rotating magnetic field drive coils located within the magnet structure. The drive coil structure is the principal source of heat because of the high frequency resistive losses in the wires that surround the chip. The temperature compensation needed by the chip (normally provided by the permanent magnet's similar temperature coefficient) is impeded by the interstitial placement of the leveling plate, causing a temperature gradient between chip and magnet.
Therefore, an object of the present invention is to eliminate the high permeability leveling plate and to create a more compact bias field magnet for a bubble memory device.